Training weapon system

ABSTRACT

The invention relates to a training weapon system for a portable recoilless anti-armor weapon of the type which comprises a sub-caliber insert barrel (1) arranged in the bore of the launching barrel of the full-caliber weapon. In order to improve the accuracy of the system and make it more safe as well as less expensive when compared to previous systems of this type, the sub-caliber insert barrel (1) has a rifled bore to make the training projectile spin stabilized. The forward aligning member (5) for centering the insert barrel (1) is engaging the ridges of the rifles in the rifled portion of the barrel in the recoilless full caliber weapon. By such an arrangement it can be avoided that length tolerances give rise to undesired radical deviations which might result in a mis-alignment of the insert barrel (1) within the gun bore. This could happen with the forward aligning member engaging the conical, smooth-bored firing chamber in the barrel.

The present invention relates to a training weapon system for a portablerecoilless anti-armour weapon of the type which comprises a sub-caliberinsert barrel arranged in the bore of the launching barrel of theanti-armour weapon. One example of a recoilless anti-armour weapon inwhich the invention can be used is the 84 mm Carl Gustaf recoilless gunm/48.

For an effective training of a specific weapon it is important that thesoldiers are permitted to fire a large number of ammunition rounds underas realistic conditions as possible. This means that the handling of theweapon and its ammunition should be as close to the real (parent) weaponas possible and the firing experience should also be as realistic aspossible. Of course, this is best achieved by allowing full-caliberammunition rounds also for the training. However, this can rarely bedone for economical and safety reasons.

Therefore, it is previously known to use sub-caliber ammunition trainingweapons. In this case the training weapon has a sub-caliber insertbarrel arranged inside the barrel of the parent weapon in question.Specifically, for an 84 mm anti-armour gun m/48 sub-caliber systems of7.62 mm, 9 mm and 20 mm caliber have been developed. One example of a 20mm caliber training weapon of this type is illustrated in SE 9400043-7.

The advantage with this type of training weapon systems is the fact thatthe soldier is allowed to fire a sub-caliber instead of an expensivefull caliber ammunition round. He can well study his ability to hit thetarget. However, in the 7.62 mm as well as in the 9 mm system, thefiring experience is quite different from the real, live conditions. Thesoldier does not experience the sudden sound and gas pressure which isgenerated in the corresponding service weapon system. In order tosimulate the specific out-blow effect at the rear of the weapon anadditional charge has to be applied in these systems. This charge isdetonated at the firing moment in order to give the soldier a morerealistic training experience with respect to the generated sound andshock waves.

The 20 mm training system, however, provides a realistic sound levelaround the weapon and this system also provides an out-blow effectbecause of its recoilless function. The sub-caliber barrel is disposedin the bore of the full-caliber weapon in a body shaped as a round ofammunition similar to the full-caliber high explosive shell. Thesub-calibre barrel is smooth-bored. However, the accuracy of such asystem is unsatisfactory as soon as the firing distance exceeds 250 m.

Furthermore, in some cases it has happened that the so-called nozzlescrew has been unscrewed at the firing and thrown rearwards with a highsafety risk for personnel behind the weapon.

Recoilless ammunition round of this type also have a plastic bottomplate member which is broken when the round is fired. When the bottomplate member is broken it is divided into small splinters which could bedangerous up to 70 m behind the weapon. This can be compared with arequired safety distance of 15 m for the service weapon under warconditions.

The object of this invention is to provide a sub-caliber weapon systemfor training purposes in which the accuracy and safety has been improvedbut at reduced cost compared to previous systems of this kind. Accordingto the invention this is achieved by providing the sub-calibre insertbarrel with a rifled bore and arranging the insert barrel so that theforward aligning member of the barrel is engaging the ridges of therifling in the rifled section of the full-caliber weapon.

In the following the invention will be described more in detail inconnection with a 20 mm training weapon system for an 84 mm gun m/48 andwhich is schematically illustrated on the accompanyed drawing.

The reason for choosing caliber 20 mm system is the fact that such asystem provides a realistic sound level around the weapon, as alreadymentioned. It also seems as if a caliber around 20 mm has an optimalcost efficiency relative to the required training and feelingexperience. The sound-level for a 20 mm system is approximately 170 dBto be compared with approximately 180 db for the full-caliber version.The duration of the sound wave (A-duration) is approximately 1/3 of thereal system and is experienced as fully satisfactory.

The training weapon comprises an insert barrel 1 for a sub-caliberprojectile. The insert barrel is mounted in a body 2 shaped as anordinary ammunition round and which is loaded in the gun in the samemanner as the ordinary full-caliber round. The body 2 has aconventional, elongated cylindrical portion 3 and a conical forwardportion 4 and a calibre of 84 mm. The insert barrel 1 is mounted in thebody 2 by means of a forward aligning member 5 for centering the barreland a rear breech block 6 with an ignition channel 7 and threads 8 forthe nozzle screw. The rear part of the barrel has a conventional firingchamber 9 for the training projectile.

As shown in FIG. 1 the axial length of the conical portion 4 is about22% of the length of the entire elongated cylindrical portion 3.

According to the invention the insert barrel 1 has a rifled bore insteadof being smooth-bored like previous training weapons of the insert type.This means that the projectile cost is reduced, as a spin stabilizedprojectile is less expensive to manufacture than a fin stabilizedprojectile. It should also be understood that for a given projectilecaliber a reduction of the air resistance is more easily achieved for aspin stabilized projectile compared to a fin stabilized projectile. Asthe training ammunition should have the same trajectory as thecorresponding live ammunition, the retardation of the projectile in eachpoint of the trajectory should be as similar to the corresponding liveprojectile as possible. This is achieved if the ratio of the projectilemass to the air resistance area is the same for the two types ofammunition units. Consequently, a spin stabilized projectile can be madewith a less projectile mass compared to a corresponding fin stabilizedprojectile. As a result the amount of powder could be reduced whichmeans a less expensive product.

The accuracy of a spin stabilized training weapon system is alsoimproved due to the inherent stability in such a system. It is wellknown that it is very difficult to provide a corresponding accuracy in afin stabilized system.

In order to further improve the accuracy of the training system theforward aligning member 5 of the weapon is engaging the ridges of therifling of the rifled portion in the bore of the gun barrel instead ofengaging the conical (not rifled) firing chamber portion of the gun likein other similar training systems. By such an arrangement it could beavoided that any length tolerances give rise to undesired radialdeviations resulting in a mis-alignment of the insert barrel in the gun.

The forward aligning member 5 is made as an annular sleeve having acircumferential portion 10 forming the contacting surface against theprojecting ridges of the rifling. The longitudinal dimension of thecontacting surface exceeds the width of a rifle groove so that thealigning member 5 bridges a rifle groove and is contacting theprojecting part (ridges) of the rifling only. By allowing the aligningmember to engage the ridges only, i.e. in the rifled portion of thebore, the aligning member can be located in a more forward positioncompared to the previous location inside the firing chamber, which isbehind the rifled portion of the gun barrel. In this case this meansthat the aligning member can be located in the most forward position onthe cylindrical portion 3 of the shell-formed body.

To prevent the nozzle screw to unscrew when the ammunition round isfired a vent hole 11 is made in the cylindrical wall of the breech blockto reduce the pressure on the nozzle screw. Any gas leakage at the rearsurface of the cartridge case can then escape through this hole insteadof passing through the threads 8, like in other systems. The risk for anunintentional unscrewing of the nozzle screw can then be eliminated.

The design of the rear portion of the weapon with the breech block, thenozzle and the screw is not part of this invention and will not bedescribed in any detail here. Nor is the ammunition round per sedescribed in this connection. In order to reduce the risk for harmfulsplinters behind the weapon, and thereby improve the safety, a bottomplate member according to SE 9501344-7 can be used. In this way thesafety distance can be reduced from 70 m to 15 m.

The invention is not limited to the training weapon which has beenillustrated here as an example, but can be varied within the scope ofthe following claims.

What is claimed is:
 1. A training weapon system for a portablerecoilless anti-armor weapon comprising a practice cartridge, saidweapon having a barrel with a rifled bore therein, said rifled borecontaining spiralled ridges, with depressed lands therebetween;saidpractice cartridge comprising a casing with a rear surface, an elongatedcylindrical portion (3) and a conical forward portion (4), and a chamberfor containing a sub-caliber projectile, said elongated cylindricalportion of said practice cartridge having a uniform outside dimensionthroughout its length equal to an ammunition round for said weapon, andfilling a chamber of the portable recoilless anti-armor weapon when itis inserted, said conical forward portion forming a uniformly inclinedline in cross-section, said conical forward portion having an axiallength of about 22% of the length of the elongated cylindrical portion,said practice cartridge having a sub-caliber insert barrel (1) with itsaxis congruent with the axis of the barrel of said weapon when saidpractice cartridge is inserted into the firing position inside of theweapon, said insert barrel (1) having a rifled bore to provide spinstabilization of the sub-caliber projectile, said practice cartridgehaving a forward aligning member (5) placed axially between and incontact with said elongated cylindrical portion and said forward conicalportion, for aligning said insert barrel inside said weapon, saidaligning member comprising an annular sleeve with a central aperturecomprising an inner circumference, and an outer circumference, saidinner circumference of said aligning member fitting around the forwardportion of said insert barrel, said outer circumference having a contactsurface (10) engaging said ridges of the rifled bore of said recoillessweapon, said contact surface having a longitudinal extension exceedingthe axial width of a rifle groove,so that the aligning member bridgesadjacent rifle grooves and is engaging only the projecting ridges ofonly the rifles of said recoilless weapon.
 2. The training weapon systemaccording to claim 1 characterised in that said sub-caliber insertbarrel (1) has a caliber of 20 mm.
 3. The training weapon system ofclaim 1 characterized in that said insert barrel is mounted at the rearof the practice cartridge in a breech block (6) with a nozzle screwthread (8).
 4. The training weapon system according to claim 3characterised by a vent hole (11) made in a cylindrical wall of thebreech block to provide an exit for a possible gas leakage.